smallest filesize for transparent single pixel image

Question

I\'m looking for the smallest (in terms of filesize) transparent 1 pixel image.

Currently I have a gif of 49 bytes which seems to be the most popular.

But I

Answer 1

Here is what I use in a C# byte array (avoids file access)

static readonly byte[] TrackingGif = { 0x47, 0x49, 0x46, 0x38, 0x39, 0x61, 0x1, 0x0, 0x1, 0x0, 0x80, 0x0, 0x0, 0xff, 0xff, 0xff, 0x0, 0x0, 0x0, 0x2c, 0x0, 0x0, 0x0, 0x0, 0x1, 0x0, 0x1, 0x0, 0x0, 0x2, 0x2, 0x44, 0x1, 0x0, 0x3b };

In asp.net MVC this can be returned like this

return File(TrackingGif, "image/gif");